This program is for predoctoral training of biological science Ph.D. students for research careers in Cellular and Molecular Biology. This interdisciplinary program involves students and 39 faculty members from the Divisions of Biology, Chemistry and Chemical Engineering, Engineering and Applied Sciences and Geological and Planetary Sciences. It is a continuation of a training program supported at Caltech for the past 25 years by NIH. Subjects of special emphasis within Cellular and Molecular Biology include genetics and genomics, regulation of gene expression, signal transduction, eukaryotic cell biology, mechanisms of development, microbial physiology, biopolymers, and protein structure and function. Interaction between the Divisions is evidenced by students who, although earning their Ph.D. in one Division, choose to carry out their thesis research mentored by a faculty member of another Division; by joint courses offered by two or more Divisions; by a large amount of less-formal interaction including research collaborations, and by a graduate program in Biochemistry. The major components of the training activities are: 1) each student's individual research program, guided by one or more faculty members and carried out within a group of other students and postdoctoral fellows having related interests; 2) a core graduate course in Biology; 3) preparation for candidacy examinations, typically involving formal courses and less-formal group study; 4) an extensive seminar program, plus many other less formal seminars and group meetings; and 5) a course and discussion in responsible conduct of research, and 6) a research seminar during which students present their own. Predoctoral trainees are admitted to graduate study in Biology, Chemistry or Biochemistry on the basis of the normal, highly selective admissions criteria used by each option, especially high quantitative aptitude and strong motivation for a research career. Trainees will be selected from admitted students, and will be those who indicate and maintain a primary interest in research in the area of Cellular and Molecular Biology. Trainees are expected to pursue research careers that require training in Cellular and Molecular Biology; the superb record of our past trainees supports this expectation. Facilities for this program are located in a complex of ten adjacent buildings two others. Multi-user facilities include those for cell sorting, biological imaging, NMR spectroscopy, mass spectrometry, monoclonal antibody production, molecular graphics, protein and DNA sequencing, animal care and production of transgenic mice.